The present invention relates to a crimping ring comprising a rolled-up piece of metal strip whose two ends include respective first and second connection means that co-operate with each other to interconnect said ends.
A crimping ring is known, e.g. from patent application GB 2 247 041, that is made from a rolled-up piece of metal strip, with the ends of the piece being cut out in such a manner as to present complementary profiles, for example one end having a T-shaped extension while the other end has a cutout of complementary shape. These ends are engaged one in the other and thereafter they need to be fixed together permanently, e.g. by welding.
A crimping ring is sometimes subjected to extremely high stresses, particularly during the crimping operation which is performed in order to obtain the desired degree of clamping around the object to be clamped, e.g. a bellows for a universal joint.
The type of connection mentioned above is poor at withstanding particularly high stresses, specifically when the stress acts in a direction other than the longitudinal direction of the strip. This applies in particular to stresses acting perpendicularly or substantially perpendicularly to the plane of the strip.
Document EP 0 610 108 discloses a crimping ring made from a metal strip whose ends are of a thickness that is close to half the thickness of the strip itself, and whose ends having fixing studs, for example. To connect those ends together, a fixing plate having holes, for example, is used with the plate being positioned so that the studs at the ends of the strip engage in the holes in the plate. Thereafter, the free ends of the studs are riveted to the plate.
That type of connection withstands relatively high stresses in satisfactory manner. However it suffers from the drawback of requiring the use of a piece that is separate from the piece of strip. The plate therefore needs to be machined separately, and stored appropriately in supply stores, and a tool must be provided enabling it to be put into place at the ends of the strip.
Thus the presence of such a plate increases the cost of the crimping ring.
Furthermore, when stresses act in the connection zone, reaction forces bear firstly between a first end of the strip and the plate, and secondly between the second end of the strip and the plate. In other words, these forces do not act to any significant extent between the two ends of the strip themselves. In some cases where stresses are particularly high, this can result in one end being slightly offset relative to the other.
An object of the present invention is to propose a crimping ring that is simple and inexpensive to make, and that is suitable for overcoming the above-mentioned drawbacks.
This object is achieved by the fact that the first connection means comprise a first overlap surface formed in the first end of the piece of strip as a setback from the first face of said piece of strip, together with at least one female member recessed from said first overlap surface, while the second connection means comprises a second overlap surface formed in the second end of the piece of strip as a setback from the second face of said piece of strip, together with a male member projecting from said second overlap surface, and in that the male member is engaged in the female member and fixed thereto while the overlap surfaces are placed one against the other so as to define a connection zone whose thickness is substantially equal to the thickness of the main portion of the piece of strip.
It will be understood that with the invention the two connected-together ends of the strip are in contact with each other via a relatively large area, corresponding to the areas of the overlap surfaces. As a result, the stresses acting in the connection zone apply to an area that is very considerably greater than for the crimping ring of document GB 2 247 041. This leads to much more uniform distribution of the stresses and to much greater strength in the connection zone.
In particular, since the overlap surfaces are placed one against the other, they provide a high level of resistance to stresses acting in a direction other than the longitudinal direction of the strip.
Compared with the crimping ring disclosed in document EP 0 610 108, the ring of the present invention presents the advantage of avoiding the presence of an additional plate. In addition, the connection establishes close and direct contact between the two ends of the strip.
Advantageously, at least one of the first and second overlap surfaces is formed in a setback which has a wedging rim, while the outline of the other one of the overlap surfaces presents a wedging edge co-operating with said rim to oppose forces directed transversely relative to the piece of strip.
The co-operation between the wedging edge and the wedging rim enables the connection to withstand forces acting substantially in the plane of the strip, but in a direction that crosses the longitudinal direction of the strip. This co-operation is additional to the engagement of the male member in the female member and increases the strength of the connection against stresses tending to cause the two ends of the strip to pivot about an axis corresponding to a diameter of the ring.
Advantageously, the female member is formed by a through opening in the piece of strip extending from the first overlap surface.
Thus, the female member(s) can be constituted merely by an opening or a notch formed in the end of the strip, e.g. by punching. The male member can pass through the opening and can be riveted into it.
The invention also provides a method of manufacturing a crimping ring in which first and second connection means are formed respectively at the first and second ends of a piece of metal strip, and in which these ends are connected together by making said first and second connection means co-operate with each other.
The invention seeks to provide a manufacturing method enabling a crimping ring to be made that overcomes the drawbacks of the cited prior art in simple manner.
This object is achieved by the fact that a first setback is formed in the first end of the piece of strip from the first face thereof, the surface of the first setback defining a first overlap surface, at least one female member is recessed from said first overlap surface, a second setback is formed in the second end of the piece of strip from the second face thereof, the surface of this second setback defining a second overlap surface, at least one male member is formed to project from said second overlap surface, the overlap surfaces are placed one against the other, the male member is engaged in the female member, and said male member is fixed to said female member, and in that the first and second setbacks are made in such a manner that the thickness of the ring in the connection zone defined by the overlap surfaces disposed one against the other is substantially equal to the thickness of the main portion of the piece of strip.
The setbacks at the two ends of the strip are made, for example, by localized stamping or embossing. As explained below, these setbacks can be made simultaneously or one after the other. In order to engage the male member in the female member, the two ends of the strip are brought together until they are overlapping. This can be done, for example, after a stage in which the piece of strip is rolled up.
Advantageously, a female member is made as a through hole in the piece of strip, the ends of the strip are connected together so that a male member appears in said female member, and said male member is deformed in order to be fixed to said female member.